Many of the medical care garments and products, protective wear garments, mortuary and veterinary products, and personal care products in use today are partially or wholly constructed of nonwoven materials. Examples of such products include, but are not limited to, medical and health care products such as surgical drapes, gowns and bandages, protective workwear garments such as coveralls and lab coats, and infant, child and adult personal care absorbent articles such as diapers, training pants, disposable swimwear, incontinence garments and pads, sanitary napkins, wipes and the like. For these applications nonwoven fibrous webs provide functional, tactile, comfort and aesthetic properties which can approach or even exceed those of traditional woven or knitted cloth materials. Nonwoven materials are also widely utilized as filtration media for both liquid and gas or air filtration applications since they can be formed into a lofty filter mesh of fibers having a low average pore size suitable for trapping particulate matter while still having a low pressure drop across the mesh.
The characteristics or physical properties of nonwoven web materials are controlled, at least in part, by the density or openness of the fabric. The web density can be controlled to a great deal by the fiber structure and, in particular, by the curl or crimp of a fiber along its length. Generally speaking, nonwoven webs made from crimped fibers have a lower density, higher loft and improved resiliency compared to similar nonwoven webs of uncrimped fibers. Such lofty, low density webs exhibit cloth-like textural properties, e.g., softness, drapability and hand. Various methods of crimping melt-spun multicomponent fibers are known in the art. As disclosed in U.S. Pat. Nos. 3,595,731 and 3,423,266 to Davies et al., bicomponent fibers may be mechanically crimped and the resultant fibers formed into a nonwoven web or, if the appropriate polymers are used, a latent helical crimp produced in bicomponent fibers may be activated by heat treatment of the formed web. Alternatively, the methods disclosed in U.S. Pat. No. 5,382,400 to Pike et al., may be used to produce crimp in the fibers by using the differential rates of expansion and contraction of the two (or more) polymers to produce latent helical crimp in the fibers, and using a heat treatment to activate the latent helical crimp in the fibers before the fibers have been formed into a nonwoven web. In addition, U.S. Pat. No. 5,876,840 to Ning et al. teaches spunbond multicomponent fibers having a non-ionic surfactant additive within one of the components in order to accelerate its solidification rate. By adding the non-ionic surfactant to one of the components of the multicomponent fiber it is possible to develop and activate a latent crimp by drawing with unheated air.
Notwithstanding the foregoing, there is a continuing need for crimped multicomponent fibers and nonwoven fabrics made therefrom having desirable physical attributes or properties such as softness, resiliency, strength, high porosity and overall uniformity.